@knro: I made a couple of small changes to the skywatcherAltAz driver to get it working with my AZ-EQ6. I compiled the changed version according to the instructions on github. I ran these new versions on a plain raspbian system (most recent buster). Because nothing else astronomy related is on that system, I started indiserver with the changed drivers and connected KStars from my PC to that remote system. Everything worked well. But I want to apply these changes to my Stellarmate OS, also. I first tried to just copy the binary from /usr/bin from my raspbian system to Stellarmate. I did also chmod and chown the indi_skywatcherAltAz, but I already was sceptical as I noticed that my newly compiled binary has 584k and the respective binary in the Stellarmate OS only 90k. I guess, all dependencies are built into my binary and since only indi core is on that system it came out bigger ? Anyhow, the copied binary did not work within the Stellarmate OS. It did just crash. Could you pls. give a brief instruction what I have to do, to compile these drivers on my Stellarmate OS so that they also run on Stellarmate ?
Many thanks !

According to my notes, when I want to compile and run indi on Raspberry Pi OS, I do the following on my Raspberry Pi. You might want to double-check the install dependencies.
After you run the 'make install' commands, then stellarmate should run the new binaries.

@hy: thank you very much for your advice ! Tried to follow the instructions. This is what happened:

a) after recompiling (I just deleted every file within ~/Projects/build/indi-core and ran the cmake, etc. again (do I actually have to do this or can I just run the cmake, etc. without deleting the files in "../indi-core" beforehand ?) my indi_skywatcherAltAzMount binary still stands at 584k vs 90k in the "orignal Stellarmate" installation. Why is this ? It is not that I changed / added much code, it was just minor changes.

b) the "sudo apt install libavcodec-dev libavutil-dev libgphoto2-dev libdc1394-dev libgps-dev" ended with an error message "unable to locate package: libdc1394-dev". I removed this package from the command and the remaining packages have been installed

c) after the "cmake -DCMAKE_INSTALL_PREFIX=/usr -DCMAKE_BUILD_TYPE=Debug -DBUILD_LIBS=1 ~/Projects/indi-3rdparty" I received another error message: CMake Error at cmake_modules/FindFTDI1.cmake:50 (message): FTDI not found. Please install libftdil1-dev
I tried to install this package with "sudo apt install libftdil-dev; this command ended with the error message "unable to locate package libftdil-dev". I than googled this package and found "libftdi-dev", instead. Installed this package with "sudo apt install libftdi-dev", but after the cmake command I receive the same error message, as before: Please install libftdil1-dev. This is, where I am stuck, now.

What now ?

Many thanks and kind regards

I reverted to the github indi-3rdparty instructions. The dependencies are as follows:
sudo apt-get -y install libnova-dev libcfitsio-dev libusb-1.0-0-dev zlib1g-dev libgsl-dev build-essential cmake git libjpeg-dev libcurl4-gnutls-dev libtiff-dev libfftw3-dev libftdi-dev libgps-dev libraw-dev libdc1394-22-dev libgphoto2-dev libboost-dev libboost-regex-dev librtlsdr-dev liblimesuite-dev libftdi1-dev libavcodec-dev libavdevice-dev

With these, the compilation according to your instructions worked. Many thanks !

The different binary code size is most probably caused by the symbols in your code. If you "strip" your binary, it will be close to the "original Stellarmate" size.

The more I work with linux, the more I realize how little I know. Did the strip-all of my bin file. It came out at 174k (down from 584k), but still almost double the size of the stellarmate or astroberry version. What else could I do, to shrink it ? Is there any option I can use for compilation to get the smallest possible binary ?

The impact of symbols is very strong but there are more parameters with impact on binary size (see e.g. interrupt.memfault.com/blog/best-firmware-size-tools).